Hydroxychloroquine
A 4-aminoquinoline used mainly for rheumatoid arthritis and lupus, and also to treat and prevent sensitive malaria.
Also called HCQ (abbreviation).
Drug card
- Class
- 4-aminoquinoline
- How it works
- Blocking the parasite from turning toxic heme into harmless crystals
- Used for
- Rheumatoid arthritis
- Systemic and discoid lupus erythematosus
- Malaria from chloroquine-sensitive parasites
- Preventing malaria where there is no resistance
- Known for
- Retinal damage, linked to total dose and duration
- Long QT and ventricular arrhythmias
- Its name
- -quine means a quinoline drug, often an antimalarial
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does hydroxychloroquine work?
Against malaria it works like chloroquine, blocking heme polymerization in blood-stage parasites. In rheumatic disease its action is not fully known: it collects in lysosomes and raises their pH, and it appears to damp down antigen processing and cytokine production by immune cells.
Like other 4-aminoquinolines: These drugs concentrate in the parasite's acidic food vacuole and stop toxic heme from being polymerized into harmless crystals (hemozoin), so free heme builds up and kills the parasite. They act on blood stages only, not on liver hypnozoites or gametocytes, and resistance is widespread in P. falciparum. How hydroxychloroquine calms rheumatoid arthritis and lupus is not fully known.
Uses
What is hydroxychloroquine used for?
- Rheumatoid arthritis
- Systemic and discoid lupus erythematosus
- Malaria from chloroquine-sensitive parasites
- Preventing malaria where there is no resistance
Side effects
Side effects of hydroxychloroquine
- Retinal damage, linked to total dose and durationKnown forSerious
- Long QT and ventricular arrhythmiasKnown forSerious
- Nausea, vomiting, diarrhea and abdominal pain
- Rash and itching
- Cardiomyopathy and heart failureSerious
- Low blood sugar (hypoglycemia)Serious
- Hemolysis in G6PD deficiencySerious
- Muscle weakness (myopathy) and neuropathySerious
- Mood changes, psychosis and suicidal thoughtsSerious
- Bone marrow suppressionSerious
- Severe skin reactions such as SJS, TEN and DRESSSerious
- Hearing loss, tinnitus and vertigoSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Baseline and regular retinal exams are needed: the risk rises with total dose and years of use.
- Avoid in long QT or with other QT-prolonging drugs; correct low potassium and magnesium first.
- It can lower blood sugar, so insulin or other antidiabetic doses may need reducing.
- Avoid in psoriasis and porphyria, which it can worsen.
Good to know: The 4-aminoquinoline used for long-term rheumatic disease. Retinal damage rises with total dose and years of use, so regular eye screening is part of long-term treatment.
Remember it
A way to remember it
Chloroquine stops the parasite taking out its trash.
The parasite must lock toxic heme away as harmless crystals (hemozoin). 4-aminoquinolines gather in its acidic food vacuole and block this, so free heme poisons it.
Written for biofideX
Its name
-quine means quinoline drug, often an antimalarial
Chloroquine, hydroxychloroquine, primaquine and mefloquine are antimalarials, but debrisoquine and oxamniquine, also quinolines, are not.
- Every drug name stem
Its class
4-aminoquinolines
Other 4-aminoquinolines with a card:
Easily mixed up with 8-aminoquinolines and artemisinins.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Antifungals and antiparasitics
Hydroxychloroquine is one of 14 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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